this is my outdoor box turtle pen. I made it of cement backer board (from Lowes) cut in half lengthwise for the sides, attached together with zip ties. To prevent digging out, I use 1"x2" boards with 9" galvanized nails through the board every 2.5" and driven into the ground. I don't use any type of cover since I don't have a critter problem. (I did add some fencing to give additional height to detere my cocker spaniel from jumping in.) It gets part sun and plenty of shade. Lots of grass and weeds grow along with volunteer tomatoe, squash and strawberry plants. I provide lots of pine straw and hides also. The pen is easily expandable by adding or moving the cement sides and nail boards. I have attached a mister to simulate rain on dryr days. The turtles love the mister!